1. Technical Field
The present invention relates to pneumatic cleaning modules, and more particularly, to a pneumatic cleaning module for a magnetic ruler of a position measurement system.
2. Description of Related Art
FIGS. 1 and 2 depict basic structure of a position measurement system that comprises a magnetic ruler 50 affixed to a machine by an adhesive and a displacement transducer 60 designed to move along a surface of the magnetic ruler 50. While the position measurement system may be implemented for cutting works, it sometimes confronts oil or water during operation and the adhesive that attaches the magnetic ruler 50 to the machine tends to deteriorate or become totally invalid after long-term washout. Consequently, the magnetic ruler 50 may loosen from and come off the machine. To avoid this, the magnetic ruler 50 is preferably to be as isolated as possible from direct contact with the cutting oil or water. Or, the cutting oil or water spraying over the magnetic ruler 50 must be removed as soon as possible. Besides, as the magnetic ruler 50 in nature attracts ferroic substances, when a workpiece processed by the machine contains iron or other ferroic substances, some swarf of the workpiece may be caught by the magnetic ruler 50 and bring interference to the position measurement system in its measurement.
One known solution for preventing the said problems is to provide the displacement transducer 60 at its bottom with a scraper 61 that contacts the surface of the magnetic ruler 50 so that when the displacement transducer 60 moves, the scraper 61 serves to scrape off the cutting swarf and cutting oil from the surface of the magnetic ruler 50.
Such conventional cleaning module for a magnetic ruler of a position measurement system nevertheless has some drawbacks. That is, after lasting out friction with the magnetic ruler 50 for a certain period of time, the scraper 61 tends to suffer from inferior scraping effect caused by deterioration and deformation thereof. Eventually, the scraper 61 can become invalid to competently remove the swarf and cutting oil from the surface on the magnetic ruler 50. Or what is worse, the deteriorated scraper 61 can generate flakes or dust that may accumulate on the surface of the magnetic ruler 50 and adversely affect the accuracy of the position measurement system. Therefore, it is important to periodically replace the scraper 61 at the bottom of the displacement transducer 60.
While first recesses 601 are provided at a lower end of the displacement transducer 60, the scraper 61 has protrusions 611 at an upper end thereof for being engaged by the first recesses 601. However, since the displacement transducer 60 and the magnetic ruler 50 of the conventional device are settled closely with merely a narrow interval therebetween, replacement of the scraper 61 is unmanageable.